1 <chapter name="Higgs Processes">
3 <h2>Higgs Processes</h2>
5 This page documents Higgs production within and beyond the Standard Model
6 (SM and BSM for short). This includes several different processes and,
7 for the BSM scenarios, a large set of parameters that would only be fixed
8 within a more specific framework such as MSSM. Two choices can be made
9 irrespective of the particular model:
11 <flag name="Higgs:cubicWidth" default="off">
12 The partial width of a Higgs particle to a pair of gauge bosons,
13 <ei>W^+ W^-</ei> or <ei>Z^0 Z^0</ei>, depends cubically on the
14 Higgs mass. When selecting the Higgs according to a Breit-Wigner,
15 so that the actual mass <ei>mHat</ei> does not agree with the
16 nominal <ei>m_Higgs</ei> one, an ambiguity arises which of the
17 two to use <ref>Sey95</ref>. The default is to use a linear
18 dependence on <ei>mHat</ei>, i.e. a width proportional to
19 <ei>m_Higgs^2 * mHat</ei>, while <code>on</code> gives a
20 <ei>mHat^3</ei> dependence. This does not affect the widths to
21 fermions, which only depend linearly on <ei>mHat</ei>.
22 This flag is used both for SM and BSM Higgses.
25 <flag name="Higgs:runningLoopMass" default="on">
26 The partial width of a Higgs particle to a pair of gluons or photons,
27 or a <ei>gamma Z^0</ei> pair, proceeds in part through quark loops,
28 mainly <ei>b</ei> and <ei>t</ei>. There is some ambiguity what kind
29 of masses to use. Default is running MSbar ones, but alternatively
30 fixed pole masses are allowed (as was standard in PYTHIA 6), which
31 typically gives a noticeably higher cross section for these channels.
32 (For a decay to a pair of fermions, such as top, the running mass is
33 used for couplings and the fixed one for phase space.)
36 <h3>Standard-Model Higgs, basic processes</h3>
38 This section provides the standard set of processes that can be
39 run together to provide a reasonably complete overview of possible
40 production channels for a single SM Higgs.
41 The main parameter is the choice of Higgs mass, which can be set in the
42 normal <code>ParticleDataTable</code> database; thereafter the properties
43 within the SM are essentially fixed.
45 <flag name="HiggsSM:all" default="off">
46 Common switch for the group of Higgs production within the Standard Model.
49 <flag name="HiggsSM:ffbar2H" default="off">
50 Scattering <ei>f fbar -> H^0</ei>, where <ei>f</ei> sums over available
51 flavours except top. Related to the mass-dependent Higgs point coupling
52 to fermions, so at hadron colliders the bottom contribution will
57 <flag name="HiggsSM:gg2H" default="off">
58 Scattering <ei>g g -> H^0</ei> via loop contributions primarily from
63 <flag name="HiggsSM:gmgm2H" default="off">
64 Scattering <ei>gamma gamma -> H^0</ei> via loop contributions primarily
65 from top and <ei>W</ei>.
69 <flag name="HiggsSM:ffbar2HZ" default="off">
70 Scattering <ei>f fbar -> H^0 Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
75 <flag name="HiggsSM:ffbar2HW" default="off">
76 Scattering <ei>f fbar -> H^0 W^+-</ei> via <ei>s</ei>-channel <ei>W^+-</ei>
81 <flag name="HiggsSM:ff2Hff(t:ZZ)" default="off">
82 Scattering <ei>f f' -> H^0 f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
86 <flag name="HiggsSM:ff2Hff(t:WW)" default="off">
87 Scattering <ei>f_1 f_2 -> H^0 f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
91 <flag name="HiggsSM:gg2Httbar" default="off">
92 Scattering <ei>g g -> H^0 t tbar</ei> via <ei>t tbar</ei> fusion
93 (or, alternatively put, Higgs radiation off a top line).
94 Warning: unfortunately this process is rather slow, owing to a
95 lengthy cross-section expression and inefficient phase-space selection.
99 <flag name="HiggsSM:qqbar2Httbar" default="off">
100 Scattering <ei>q qbar -> H^0 t tbar</ei> via <ei>t tbar</ei> fusion
101 (or, alternatively put, Higgs radiation off a top line).
102 Warning: unfortunately this process is rather slow, owing to a
103 lengthy cross-section expression and inefficient phase-space selection.
107 <h3>Standard-Model Higgs, further processes</h3>
109 A number of further production processes has been implemented, that
110 are specializations of some of the above ones to the high-<ei>pT</ei>
111 region. The sets therefore could not be used simultaneously
112 without unphysical doublecounting, as further explained below.
113 They are not switched on by the <code>HiggsSM:all</code> flag, but
114 have to be switched on for each separate process after due consideration.
117 The first three processes in this section are related to the Higgs
118 point coupling to fermions, and so primarily are of interest for
119 <ei>b</ei> quarks. It is here useful to begin by reminding that
120 a process like <ei>b bbar -> H^0</ei> implies that a <ei>b/bbar</ei>
121 is taken from each incoming hadron, leaving behind its respective
122 antiparticle. The initial-state showers will then add one
123 <ei>g -> b bbar</ei> branching on either side, so that effectively
124 the process becomes <ei>g g -> H0 b bbar</ei>. This would be the
125 same basic process as the <ei>g g -> H^0 t tbar</ei> one used for top.
126 The difference is that (a) no PDF's are defined for top and
127 (b) the shower approach would not be good enough to provide sensible
128 kinematics for the <ei>H^0 t tbar</ei> subsystem. By contrast, owing
129 to the <ei>b</ei> being much lighter than the Higgs, multiple
130 gluon emissions must be resummed for <ei>b</ei>, as is done by PDF's
131 and showers, in order to obtain a sensible description of the total
132 production rate, when the <ei>b</ei> quarks predominantly are produced
133 at small <ei>pT</ei> values.
135 <flag name="HiggsSM:qg2Hq" default="off">
136 Scattering <ei>q g -> H^0 q</ei>. This process gives first-order
137 corrections to the <ei>f fbar -> H^0</ei> one above, and should only be
138 used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> H^0</ei>
139 should be used for inclusive production. Only the dominant <ei>c</ei>
140 and <ei>b</ei> contributions are included, and generated separately
141 for technical reasons. Note that another first-order process would be
142 <ei>q qbar -> H^0 g</ei>, which is not explicitly implemented here,
143 but is obtained from showering off the lowest-order process. It does not
144 contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
145 interesting for many applications.
149 <flag name="HiggsSM:gg2Hbbbar" default="off">
150 Scattering <ei>g g -> H^0 b bbar</ei>. This process is yet one order
151 higher of the <ei>b bbar -> H^0</ei> and <ei>b g -> H^0 b</ei> chain,
152 where now two quarks should be required above some large <ei>pT</ei>
154 Warning: unfortunately this process is rather slow, owing to a
155 lengthy cross-section expression and inefficient phase-space selection.
159 <flag name="HiggsSM:qqbar2Hbbbar" default="off">
160 Scattering <ei>q qbar -> H^0 b bbar</ei> via an <ei>s</ei>-channel
161 gluon, so closely related to the previous one, but typically less
162 important owing to the smaller rate of (anti)quarks relative to
164 Warning: unfortunately this process is rather slow, owing to a
165 lengthy cross-section expression and inefficient phase-space selection.
170 The second set of processes are predominantly first-order corrections
171 to the <ei>g g -> H^0</ei> process, again dominated by the top loop.
172 We here only provide the kinematical expressions obtained in the
173 limit that the top quark goes to infinity, but scaled to the
174 finite-top-mass coupling in <ei>g g -> H^0</ei>. (Complete loop
175 expressions are available e.g. in PYTHIA 6.4 but are very lengthy.)
176 This provides a reasonably accurate description for "intermediate"
177 <ei>pT</ei> values, but fails when the <ei>pT</ei> scale approaches
180 <flag name="HiggsSM:gg2Hg(l:t)" default="off">
181 Scattering <ei>g g -> H^0 g</ei> via loop contributions primarily
186 <flag name="HiggsSM:qg2Hq(l:t)" default="off">
187 Scattering <ei>q g -> H^0 q</ei> via loop contributions primarily
188 from top. Not to be confused with the <code>HiggsSM:bg2Hb</code>
189 process above, with its direct fermion-to-Higgs coupling.
193 <flag name="HiggsSM:qqbar2Hg(l:t)" default="off">
194 Scattering <ei>q qbar -> H^0 g</ei> via an <ei>s</ei>-channel gluon
195 and loop contributions primarily from top. Is strictly speaking a
196 "new" process, not directly derived from <ei>g g -> H^0</ei>, and
197 could therefore be included in the standard mix without doublecounting,
198 but is numerically negligible.
202 <h3>Beyond-the-Standard-Model Higgs, introduction</h3>
204 Further Higgs multiplets arise in a number of scenarios. We here
205 concentrate on the MSSM scenario with two Higgs doublets, but with
206 flexibility enough that also other two-Higgs-doublet scenarios could
207 be represented by a suitable choice of parameters. Conventionally the
208 Higgs states are labelled <ei>h^0, H^0, A^0</ei> and <ei>H^+-</ei>.
209 If the scalar and pseudocalar states mix the resulting states are
210 labelled <ei>H_1^0, H_2^0, H_3^0</ei>. In process names and parameter
211 explanations both notations will be used, but for settings labels
212 we have adapted the shorthand hybrid notation <code>H1</code> for
213 <ei>h^0(H_1^0)</ei>, <code>H2</code> for <ei>H^0(H_2^0)</ei> and
214 <code>A3</code> for <ei>A^0(H_3^0)</ei>. (Recall that the
215 <code>Settings</code> database does not distinguish upper- and lowercase
216 characters, so that the user has one thing less to worry about, but here
217 it causes probles with <ei>h^0</ei> vs. <ei>H^0</ei>.) We leave the issue
218 of mass ordering between <ei>H^0</ei> and <ei>A^0</ei> open, and thereby
219 also that of <ei>H_2^0</ei> and <ei>H_3^0</ei>.
221 <flag name="Higgs:useBSM" default="off">
222 Master switch to initialize and use the two-Higgs-doublet states.
223 If off, only the above SM Higgs processes can be used, with couplings
224 as predicted in the SM. If on, only the below BSM Higgs processes can
225 be used, with couplings that can be set freely, also found further down
229 <h3>Beyond-the-Standard-Model Higgs, basic processes</h3>
231 This section provides the standard set of processes that can be
232 run together to provide a reasonably complete overview of possible
233 production channels for a single neutral Higgs state in a two-doublet
234 scenarios such as MSSM. The list of processes for neutral states closely
235 mimics the one found for the SM Higgs. Some of the processes
236 vanish for a pure pseudoscalar <ei>A^0</ei>, but are kept for flexiblity
237 in cases of mixing with the scalar <ei>h^0</ei> and <ei>H^0</ei> states,
238 or for use in the context of non-MSSM models. This should work well to
239 represent e.g. that a small admixture of the "wrong" parity would allow
240 a process such as <ei>q qbar -> A^0 Z^0</ei>, which otherwise is forbidden.
241 However, note that the loop integrals e.g. for <ei>g g -> h^0/H^0/A^0</ei>
242 are hardcoded to be for scalars for the former two particles and for a
243 pseudoscalar for the latter one, so absolute rates would not be
244 correctly represented in the case of large scalar/pseudoscalar mixing.
246 <flag name="HiggsBSM:all" default="off">
247 Common switch for the group of Higgs production beyond the Standard Model,
251 <h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
253 <flag name="HiggsBSM:allH1" default="off">
254 Common switch for the group of <ei>h^0(H_1^0)</ei> production processes.
257 <flag name="HiggsBSM:ffbar2H1" default="off">
258 Scattering <ei>f fbar -> h^0(H_1^0)</ei>, where <ei>f</ei> sums over available
263 <flag name="HiggsBSM:gg2H1" default="off">
264 Scattering <ei>g g -> h^0(H_1^0)</ei> via loop contributions primarily from
269 <flag name="HiggsBSM:gmgm2H1" default="off">
270 Scattering <ei>gamma gamma -> h^0(H_1^0)</ei> via loop contributions primarily
271 from top and <ei>W</ei>.
275 <flag name="HiggsBSM:ffbar2H1Z" default="off">
276 Scattering <ei>f fbar -> h^0(H_1^0) Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
281 <flag name="HiggsBSM:ffbar2H1W" default="off">
282 Scattering <ei>f fbar -> h^0(H_1^0) W^+-</ei> via <ei>s</ei>-channel <ei>W^+-</ei>
287 <flag name="HiggsBSM:ff2H1ff(t:ZZ)" default="off">
288 Scattering <ei>f f' -> h^0(H_1^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
292 <flag name="HiggsBSM:ff2H1ff(t:WW)" default="off">
293 Scattering <ei>f_1 f_2 -> h^0(H_1^0) f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
297 <flag name="HiggsBSM:gg2H1ttbar" default="off">
298 Scattering <ei>g g -> h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei> fusion
299 (or, alternatively put, Higgs radiation off a top line).
300 Warning: unfortunately this process is rather slow, owing to a
301 lengthy cross-section expression and inefficient phase-space selection.
305 <flag name="HiggsBSM:qqbar2H1ttbar" default="off">
306 Scattering <ei>q qbar -> h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei> fusion
307 (or, alternatively put, Higgs radiation off a top line).
308 Warning: unfortunately this process is rather slow, owing to a
309 lengthy cross-section expression and inefficient phase-space selection.
313 <h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
315 <flag name="HiggsBSM:allH2" default="off">
316 Common switch for the group of <ei>H^0(H_2^0)</ei> production processes.
319 <flag name="HiggsBSM:ffbar2H2" default="off">
320 Scattering <ei>f fbar -> H^0(H_2^0)</ei>, where <ei>f</ei> sums over available
325 <flag name="HiggsBSM:gg2H2" default="off">
326 Scattering <ei>g g -> H^0(H_2^0)</ei> via loop contributions primarily from
331 <flag name="HiggsBSM:gmgm2H2" default="off">
332 Scattering <ei>gamma gamma -> H^0(H_2^0)</ei> via loop contributions primarily
333 from top and <ei>W</ei>.
337 <flag name="HiggsBSM:ffbar2H2Z" default="off">
338 Scattering <ei>f fbar -> H^0(H_2^0) Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
343 <flag name="HiggsBSM:ffbar2H2W" default="off">
344 Scattering <ei>f fbar -> H^0(H_2^0) W^+-</ei> via <ei>s</ei>-channel <ei>W^+-</ei>
349 <flag name="HiggsBSM:ff2H2ff(t:ZZ)" default="off">
350 Scattering <ei>f f' -> H^0(H_2^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
354 <flag name="HiggsBSM:ff2H2ff(t:WW)" default="off">
355 Scattering <ei>f_1 f_2 -> H^0(H_2^0) f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
359 <flag name="HiggsBSM:gg2H2ttbar" default="off">
360 Scattering <ei>g g -> H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei> fusion
361 (or, alternatively put, Higgs radiation off a top line).
362 Warning: unfortunately this process is rather slow, owing to a
363 lengthy cross-section expression and inefficient phase-space selection.
367 <flag name="HiggsBSM:qqbar2H2ttbar" default="off">
368 Scattering <ei>q qbar -> H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei> fusion
369 (or, alternatively put, Higgs radiation off a top line).
370 Warning: unfortunately this process is rather slow, owing to a
371 lengthy cross-section expression and inefficient phase-space selection.
374 <h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
376 <flag name="HiggsBSM:allA3" default="off">
377 Common switch for the group of <ei>A^0(H_3^0)</ei> production processes.
380 <flag name="HiggsBSM:ffbar2A3" default="off">
381 Scattering <ei>f fbar -> A^0(H_3^0)</ei>, where <ei>f</ei> sums over available
386 <flag name="HiggsBSM:gg2A3" default="off">
387 Scattering <ei>g g -> A^0(A_3^0)</ei> via loop contributions primarily from
392 <flag name="HiggsBSM:gmgm2A3" default="off">
393 Scattering <ei>gamma gamma -> A^0(A_3^0)</ei> via loop contributions primarily
394 from top and <ei>W</ei>.
398 <flag name="HiggsBSM:ffbar2A3Z" default="off">
399 Scattering <ei>f fbar -> A^0(A_3^0) Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
404 <flag name="HiggsBSM:ffbar2A3W" default="off">
405 Scattering <ei>f fbar -> A^0(A_3^0) W^+-</ei> via <ei>s</ei>-channel <ei>W^+-</ei>
410 <flag name="HiggsBSM:ff2A3ff(t:ZZ)" default="off">
411 Scattering <ei>f f' -> A^0(A_3^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
415 <flag name="HiggsBSM:ff2A3ff(t:WW)" default="off">
416 Scattering <ei>f_1 f_2 -> A^0(A_3^0) f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
420 <flag name="HiggsBSM:gg2A3ttbar" default="off">
421 Scattering <ei>g g -> A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei> fusion
422 (or, alternatively put, Higgs radiation off a top line).
423 Warning: unfortunately this process is rather slow, owing to a
424 lengthy cross-section expression and inefficient phase-space selection.
428 <flag name="HiggsBSM:qqbar2A3ttbar" default="off">
429 Scattering <ei>q qbar -> A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei> fusion
430 (or, alternatively put, Higgs radiation off a top line).
431 Warning: unfortunately this process is rather slow, owing to a
432 lengthy cross-section expression and inefficient phase-space selection.
435 <h4>4) <ei>H+-</ei> processes</h4>
437 <flag name="HiggsBSM:allH+-" default="off">
438 Common switch for the group of <ei>H^+-</ei> production processes.
441 <flag name="HiggsBSM:ffbar2H+-" default="off">
442 Scattering <ei>f fbar' -> H^+-</ei>, where <ei>f, fbar'</ei> sums over
443 available incoming flavours. Since couplings are assumed
444 generation-diagonal, in practice this means <ei>c sbar -> H^+</ei>
445 and <ei>s cbar -> H^-</ei>.
449 <flag name="HiggsBSM:bg2H+-t" default="off">
450 Scattering <ei>b g -> H^+ tbar</ei>. At hadron colliders this is the
451 dominant process for single-charged-Higgs production.
455 <h4>5) Higgs-pair processes</h4>
457 <flag name="HiggsBSM:allHpair" default="off">
458 Common switch for the group of Higgs pair-production processes.
461 <flag name="HiggsBSM:ffbar2A3H1" default="off">
462 Scattering <ei>f fbar -> A^0(H_3) h^0(H_1)</ei>.
466 <flag name="HiggsBSM:ffbar2A3H2" default="off">
467 Scattering <ei>f fbar -> A^0(H_3) H^0(H_2)</ei>.
471 <flag name="HiggsBSM:ffbar2H+-H1" default="off">
472 Scattering <ei>f fbar -> H^+- h^0(H_1)</ei>.
476 <flag name="HiggsBSM:ffbar2H+-H2" default="off">
477 Scattering <ei>f fbar -> H^+- H^0(H_2)</ei>.
481 <flag name="HiggsBSM:ffbar2H+H-" default="off">
482 Scattering <ei>f fbar -> H+ H-</ei>.
486 <h3>Beyond-the-Standard-Model Higgs, further processes</h3>
488 This section mimics the above section on "Standard-Model Higgs,
489 further processes", i.e. it contains higher-order corrections
490 to the processes already listed. The two sets therefore could not
491 be used simultaneously without unphysical doublecounting.
492 They are not controlled by any group flag, but have to be switched
493 on for each separate process after due consideration. We refer to
494 the standard-model description for a set of further comments on
497 <h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
499 <flag name="HiggsBSM:qg2H1q" default="off">
500 Scattering <ei>q g -> h^0 q</ei>. This process gives first-order
501 corrections to the <ei>f fbar -> h^0</ei> one above, and should only be
502 used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> h^0</ei>
503 should be used for inclusive production. Only the dominant <ei>c</ei>
504 and <ei>b</ei> contributions are included, and generated separately
505 for technical reasons. Note that another first-order process would be
506 <ei>q qbar -> h^0 g</ei>, which is not explicitly implemented here,
507 but is obtained from showering off the lowest-order process. It does not
508 contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
509 interesting for many applications.
513 <flag name="HiggsBSM:gg2H1bbbar" default="off">
514 Scattering <ei>g g -> h^0 b bbar</ei>. This process is yet one order
515 higher of the <ei>b bbar -> h^0</ei> and <ei>b g -> h^0 b</ei> chain,
516 where now two quarks should be required above some large <ei>pT</ei>
518 Warning: unfortunately this process is rather slow, owing to a
519 lengthy cross-section expression and inefficient phase-space selection.
523 <flag name="HiggsBSM:qqbar2H1bbbar" default="off">
524 Scattering <ei>q qbar -> h^0 b bbar</ei> via an <ei>s</ei>-channel
525 gluon, so closely related to the previous one, but typically less
526 important owing to the smaller rate of (anti)quarks relative to
528 Warning: unfortunately this process is rather slow, owing to a
529 lengthy cross-section expression and inefficient phase-space selection.
533 <flag name="HiggsBSM:gg2H1g(l:t)" default="off">
534 Scattering <ei>g g -> h^0 g</ei> via loop contributions primarily
539 <flag name="HiggsBSM:qg2H1q(l:t)" default="off">
540 Scattering <ei>q g -> h^0 q</ei> via loop contributions primarily
541 from top. Not to be confused with the <code>HiggsBSM:bg2H1b</code>
542 process above, with its direct fermion-to-Higgs coupling.
546 <flag name="HiggsBSM:qqbar2H1g(l:t)" default="off">
547 Scattering <ei>q qbar -> h^0 g</ei> via an <ei>s</ei>-channel gluon
548 and loop contributions primarily from top. Is strictly speaking a
549 "new" process, not directly derived from <ei>g g -> h^0</ei>, and
550 could therefore be included in the standard mix without doublecounting,
551 but is numerically negligible.
555 <h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
557 <flag name="HiggsBSM:qg2H2q" default="off">
558 Scattering <ei>q g -> H^0 q</ei>. This process gives first-order
559 corrections to the <ei>f fbar -> H^0</ei> one above, and should only be
560 used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> H^0</ei>
561 should be used for inclusive production. Only the dominant <ei>c</ei>
562 and <ei>b</ei> contributions are included, and generated separately
563 for technical reasons. Note that another first-order process would be
564 <ei>q qbar -> H^0 g</ei>, which is not explicitly implemented here,
565 but is obtained from showering off the lowest-order process. It does not
566 contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
567 interesting for many applications.
571 <flag name="HiggsBSM:gg2H2bbbar" default="off">
572 Scattering <ei>g g -> H^0 b bbar</ei>. This process is yet one order
573 higher of the <ei>b bbar -> H^0</ei> and <ei>b g -> H^0 b</ei> chain,
574 where now two quarks should be required above some large <ei>pT</ei>
576 Warning: unfortunately this process is rather slow, owing to a
577 lengthy cross-section expression and inefficient phase-space selection.
581 <flag name="HiggsBSM:qqbar2H2bbbar" default="off">
582 Scattering <ei>q qbar -> H^0 b bbar</ei> via an <ei>s</ei>-channel
583 gluon, so closely related to the previous one, but typically less
584 important owing to the smaller rate of (anti)quarks relative to
586 Warning: unfortunately this process is rather slow, owing to a
587 lengthy cross-section expression and inefficient phase-space selection.
591 <flag name="HiggsBSM:gg2H2g(l:t)" default="off">
592 Scattering <ei>g g -> H^0 g</ei> via loop contributions primarily
597 <flag name="HiggsBSM:qg2H2q(l:t)" default="off">
598 Scattering <ei>q g -> H^0 q</ei> via loop contributions primarily
599 from top. Not to be confused with the <code>HiggsBSM:bg2H1b</code>
600 process above, with its direct fermion-to-Higgs coupling.
604 <flag name="HiggsBSM:qqbar2H2g(l:t)" default="off">
605 Scattering <ei>q qbar -> H^0 g</ei> via an <ei>s</ei>-channel gluon
606 and loop contributions primarily from top. Is strictly speaking a
607 "new" process, not directly derived from <ei>g g -> H^0</ei>, and
608 could therefore be included in the standard mix without doublecounting,
609 but is numerically negligible.
613 <h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
615 <flag name="HiggsBSM:qg2A3q" default="off">
616 Scattering <ei>q g -> A^0 q</ei>. This process gives first-order
617 corrections to the <ei>f fbar -> A^0</ei> one above, and should only be
618 used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> A^0</ei>
619 should be used for inclusive production. Only the dominant <ei>c</ei>
620 and <ei>b</ei> contributions are included, and generated separately
621 for technical reasons. Note that another first-order process would be
622 <ei>q qbar -> A^0 g</ei>, which is not explicitly implemented here,
623 but is obtained from showering off the lowest-order process. It does not
624 contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
625 interesting for many applications.
629 <flag name="HiggsBSM:gg2A3bbbar" default="off">
630 Scattering <ei>g g -> A^0 b bbar</ei>. This process is yet one order
631 higher of the <ei>b bbar -> A^0</ei> and <ei>b g -> A^0 b</ei> chain,
632 where now two quarks should be required above some large <ei>pT</ei>
634 Warning: unfortunately this process is rather slow, owing to a
635 lengthy cross-section expression and inefficient phase-space selection.
639 <flag name="HiggsBSM:qqbar2A3bbbar" default="off">
640 Scattering <ei>q qbar -> A^0 b bbar</ei> via an <ei>s</ei>-channel
641 gluon, so closely related to the previous one, but typically less
642 important owing to the smaller rate of (anti)quarks relative to
644 Warning: unfortunately this process is rather slow, owing to a
645 lengthy cross-section expression and inefficient phase-space selection.
649 <flag name="HiggsBSM:gg2A3g(l:t)" default="off">
650 Scattering <ei>g g -> A^0 g</ei> via loop contributions primarily
655 <flag name="HiggsBSM:qg2A3q(l:t)" default="off">
656 Scattering <ei>q g -> A^0 q</ei> via loop contributions primarily
657 from top. Not to be confused with the <code>HiggsBSM:bg2H1b</code>
658 process above, with its direct fermion-to-Higgs coupling.
662 <flag name="HiggsBSM:qqbar2A3g(l:t)" default="off">
663 Scattering <ei>q qbar -> A^0 g</ei> via an <ei>s</ei>-channel gluon
664 and loop contributions primarily from top. Is strictly speaking a
665 "new" process, not directly derived from <ei>g g -> A^0</ei>, and
666 could therefore be included in the standard mix without doublecounting,
667 but is numerically negligible.
671 <h3>Parameters for Beyond-the-Standard-Model Higgs production and decay</h3>
673 This section offers a big flexibility to set couplings of the various
674 Higgs states to fermions and gauge bosons, and also to each other.
675 The intention is that, for scenarios like MSSM, you should use standard
676 input from the <aloc href="SUSYLesHouchesAccord">SUSY Les Houches
677 Accord</aloc>, rather than having to set it all yourself. In other cases,
678 however, the freedom is there for you to use. Kindly note that some
679 of the internal calculations of partial widths from the parameters provided
680 do not include mixing between the scalar and pseudoscalar states.
683 Masses would be set in the <code>ParticleDataTable</code> database,
684 while couplings are set below. When possible, the couplings of the Higgs
685 states are normalized to the corresponding coupling within the SM.
686 When not, their values within the MSSM are indicated, from which
687 it should be straightforward to understand what to use instead.
688 The exception is some couplings that vanish also in the MSSM, where the
689 normalization has been defined in close analogy with nonvanishing ones.
690 Some parameter names are asymmetric but crossing can always be used,
691 i.e. the coupling for <ei>A^0 -> H^0 Z^0</ei> obviously is also valid
692 for <ei>H^0 -> A^0 Z^0</ei> and <ei>Z^0 -> H^0 A^0</ei>.
693 Note that couplings usually appear quadratically in matrix elements.
695 <parm name="HiggsH1:coup2d" default="1.">
696 The <ei>h^0(H_1^0)</ei> coupling to down-type quarks.
699 <parm name="HiggsH1:coup2u" default="1.">
700 The <ei>h^0(H_1^0)</ei> coupling to up-type quarks.
703 <parm name="HiggsH1:coup2l" default="1.">
704 The <ei>h^0(H_1^0)</ei> coupling to (charged) leptons.
707 <parm name="HiggsH1:coup2Z" default="1.">
708 The <ei>h^0(H_1^0)</ei> coupling to <ei>Z^0</ei>.
711 <parm name="HiggsH1:coup2W" default="1.">
712 The <ei>h^0(H_1^0)</ei> coupling to <ei>W^+-</ei>.
715 <parm name="HiggsH1:coup2Hchg" default="0.">
716 The <ei>h^0(H_1^0)</ei> coupling to <ei>H^+-</ei> (in loops).
717 Is <ei>sin(beta - alpha) + cos(2 beta) sin(beta + alpha) /
718 (2 cos^2theta_W)</ei> in the MSSM.
721 <parm name="HiggsH2:coup2d" default="1.">
722 The <ei>H^0(H_2^0)</ei> coupling to down-type quarks.
725 <parm name="HiggsH2:coup2u" default="1.">
726 The <ei>H^0(H_2^0)</ei> coupling to up-type quarks.
729 <parm name="HiggsH2:coup2l" default="1.">
730 The <ei>H^0(H_2^0)</ei> coupling to (charged) leptons.
733 <parm name="HiggsH2:coup2Z" default="1.">
734 The <ei>H^0(H_2^0)</ei> coupling to <ei>Z^0</ei>.
737 <parm name="HiggsH2:coup2W" default="1.">
738 The <ei>H^0(H_2^0)</ei> coupling to <ei>W^+-</ei>.
741 <parm name="HiggsH2:coup2Hchg" default="0.">
742 The <ei>H^0(H_2^0)</ei> coupling to <ei>H^+-</ei> (in loops).
743 Is <ei>cos(beta - alpha) + cos(2 beta) cos(beta + alpha) /
744 (2 cos^2theta_W)</ei> in the MSSM.
747 <parm name="HiggsH2:coup2H1H1" default="1.">
748 The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
749 Is <ei>cos(2 alpha) cos(beta + alpha) - 2 sin(2 alpha)
750 sin(beta + alpha)</ei> in the MSSM.
753 <parm name="HiggsH2:coup2A3A3" default="1.">
754 The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0)</ei> pair.
755 Is <ei>cos(2 beta) cos(beta + alpha)</ei> in the MSSM.
758 <parm name="HiggsH2:coup2H1Z" default="0.">
759 The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
760 Vanishes in the MSSM.
763 <parm name="HiggsH2:coup2A3H1" default="0.">
764 The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0) h^0(H_1^0)</ei> pair.
765 Vanishes in the MSSM.
768 <parm name="HiggsH2:coup2HchgW" default="0.">
769 The <ei>H^0(H_2^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
770 Vanishes in the MSSM.
773 <parm name="HiggsA3:coup2d" default="1.">
774 The <ei>A^0(H_3^0)</ei> coupling to down-type quarks.
777 <parm name="HiggsA3:coup2u" default="1.">
778 The <ei>A^0(H_3^0)</ei> coupling to up-type quarks.
781 <parm name="HiggsA3:coup2l" default="1.">
782 The <ei>A^0(H_3^0)</ei> coupling to (charged) leptons.
785 <parm name="HiggsA3:coup2H1Z" default="1.">
786 The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
787 Is <ei>cos(beta - alpha)</ei> in the MSSM.
790 <parm name="HiggsA3:coup2H2Z" default="1.">
791 The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^0(H_2^0) Z^0</ei> pair.
792 Is <ei>sin(beta - alpha)</ei> in the MSSM.
795 <parm name="HiggsA3:coup2Z" default="0.">
796 The <ei>A^0(H_3^0)</ei> coupling to <ei>Z^0</ei>.
797 Vanishes in the MSSM.
800 <parm name="HiggsA3:coup2W" default="0.">
801 The <ei>A^0(H_3^0)</ei> coupling to <ei>W^+-</ei>.
802 Vanishes in the MSSM.
805 <parm name="HiggsA3:coup2H1H1" default="0.">
806 The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
807 Vanishes in the MSSM.
810 <parm name="HiggsA3:coup2Hchg" default="0.">
811 The <ei>A^0(H_3^0)</ei> coupling to <ei>H^+-</ei>.
812 Vanishes in the MSSM.
815 <parm name="HiggsA3:coup2HchgW" default="0.">
816 The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
817 Vanishes in the MSSM.
820 <parm name="HiggsHchg:tanBeta" default="5.">
821 The <ei>tan(beta)</ei> value, which leads to an enhancement of the
822 <ei>H^+-</ei> coupling to down-type fermions and suppression to
823 up-type ones. The same angle also appears in many other places,
824 but this particular parameter is only used for the charged-Higgs case.
827 <parm name="HiggsHchg:coup2H1W" default="1.">
828 The <ei>H^+-</ei> coupling to a <ei>h^0(H_1^0) W^+-</ei> pair.
829 Is <ei>cos(beta - alpha)</ei> in the MSSM.
832 <parm name="HiggsHchg:coup2H2W" default="0.">
833 The <ei>H^+-</ei> coupling to a <ei>H^0(H_2^0) W^+-</ei> pair.
834 Is <ei>1 - cos(beta - alpha)</ei> in the MSSM.
838 Another set of parameters are not used in the production stage but
839 exclusively for the description of angular distributions in decays.
841 <modepick name="HiggsH1:parity" default="1" min="0" max="3">
842 possibility to modify angular decay correlations in the decay of a
843 <ei>h^0(H_1)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
844 fermions. Currently it does not affect the partial width of the
845 channels, which is only based on the above parameters.
846 <option value="0">isotropic decays.</option>
847 <option value="1">assuming the <ei>h^0(H_1)</ei> is a pure scalar
848 (CP-even), as in the MSSM.</option>
849 <option value="2">assuming the <ei>h^0(H_1)</ei> is a pure pseudoscalar
851 <option value="3">assuming the <ei>h^0(H_1)</ei> is a mixture of the two,
852 including the CP-violating interference term. The parameter
853 <ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
854 with the interference term being proportional to <ei>eta</ei>
855 and the CP-odd one to <ei>eta^2</ei>.</option>
858 <parm name="HiggsH1:etaParity" default="0.">
859 The <ei>eta</ei> value of CP-violation in the
860 <code>HiggsSM:parity = 3</code> option.
863 <modepick name="HiggsH2:parity" default="1" min="0" max="3">
864 possibility to modify angular decay correlations in the decay of a
865 <ei>H^0(H_2)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
866 fermions. Currently it does not affect the partial width of the
867 channels, which is only based on the above parameters.
868 <option value="0">isotropic decays.</option>
869 <option value="1">assuming the <ei>H^0(H_2)</ei> is a pure scalar
870 (CP-even), as in the MSSM.</option>
871 <option value="2">assuming the <ei>H^0(H_2)</ei> is a pure pseudoscalar
873 <option value="3">assuming the <ei>H^0(H_2)</ei> is a mixture of the two,
874 including the CP-violating interference term. The parameter
875 <ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
876 with the interference term being proportional to <ei>eta</ei>
877 and the CP-odd one to <ei>eta^2</ei>.</option>
880 <parm name="HiggsH2:etaParity" default="0.">
881 The <ei>eta</ei> value of CP-violation in the
882 <code>HiggsSM:parity = 3</code> option.
885 <modepick name="HiggsA3:parity" default="2" min="0" max="3">
886 possibility to modify angular decay correlations in the decay of a
887 <ei>A^0(H_3)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
888 fermions. Currently it does not affect the partial width of the
889 channels, which is only based on the above parameters.
890 <option value="0">isotropic decays.</option>
891 <option value="1">assuming the <ei>A^0(H_3)</ei> is a pure scalar
893 <option value="2">assuming the <ei>A^0(H_3)</ei> is a pure pseudoscalar
894 (CP-odd), as in the MSSM.</option>
895 <option value="3">assuming the <ei>A^0(H_3)</ei> is a mixture of the two,
896 including the CP-violating interference term. The parameter
897 <ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
898 with the interference term being proportional to <ei>eta</ei>
899 and the CP-odd one to <ei>eta^2</ei>.</option>
902 <parm name="HiggsA3:etaParity" default="0.">
903 The <ei>eta</ei> value of CP-violation in the
904 <code>HiggsSM:parity = 3</code> option.
909 <!-- Copyright (C) 2008 Torbjorn Sjostrand -->